1. Field of the Invention
The present invention relates to an ink jet head apparatus which provides a lamination type piezoelectric actuator.
2. Description of the Related Art
The inventor of the present invention knows that there has been already proposed an ink jet head apparatus which uses a piezoelectric actuator for applying pressure onto ink. The piezoelectric actuator used in the ink jet head apparatus is arranged to have a plurality of laminated piezoelectric elements each having a signal electrode and a ground electrode formed on the opposite sides of the element itself.
The piezoelectric actuator used in the ink jet head apparatus will be described.
As mentioned above, the piezoelectric actuator is arranged to have a plurality of laminated piezoelectric elements. Each piezoelectric element includes as a main body a piezoelectric rectangular board in which distortion or stress takes place depending on the voltage applied on the piezoelectric board. The piezoelectric board provides the signal electrode on one side and the ground electrode on the opposite side. The piezoelectric actuator is, hence, structured to have the signal electrode, the ground electrode, the signal electrode, the ground electrode, the signal electrode, . . . in sequence with the piezoelectric board laid between each pair of the signal electrode and the ground electrode.
The signal electrodes are connected to each other in common and connected to the outside through a connecting conductor. The ground electrodes are connected to each other in common and connected to the outside through another connecting conductor.
As one example of the arrangement, the upper-right portion of the piezoelectric actuator is fixed on a fixing table. The left end of the piezoelectric actuator is built into the ink jet head apparatus so that the left end may face an ink chamber. When a voltage is applied between the signal electrode and the ground electrode, the left end of the piezoelectric actuator serves to press the ink chamber for applying pressure to the ink contained in the ink chamber.
The known ink jet head apparatus is arranged to expose the signal electrodes outside and to locate the connecting conductor for the signal electrode on the left side of the piezoelectric actuator facing to the ink chamber. The arrangement causes erroneous current passage in another piezoelectric actuator through the ink. To overcome this erroneous current passage, it is necessary to strictly carry out the insulating treatment on the side of the piezoelectric actuator facing to the ink chamber. Or, it is necessary to add the insulated leg portion to the left side of the piezoelectric actuator facing to the ink chamber so as to prevent the signal electrodes and the connecting conductor from coming into contact with the ink, The insulating treatment or the addition of the leg portion may result in making the overall structure more complicated, raising the manufacturing cost and lowering the reliability.